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UNITED STATES.

PATENT OFFICE.

LOUIS G. LAUREAU, OF NEW YORK, N. Y.

METHOD OF DEPHOSPHORIZING CRUDE CAST-IRON- SPECIFICATION forming part ofLetters Patent No. 246,398, dated August 30, 1881.

Application filed April 26, 1880.

To all whom it may concern:

Be it known that I, LOUIS G. LA'UREAU, of the city and State of NewYork,have invented a new and useful Improvementin the Method ofDephosphorizing Crude 0ast-Iron,of which the following is aspecification.

A brief statement of the known dephosphorizing processes, such as theBell and the. Krupp, will be necessary to the thorough understanding ofmy invention.

In the processes alluded to the impurities of the crude ca st-ironusually known as pigsuch as silicon, manganese, phosphorus, sulphur,Sac-are oxidized at a low temperature in a revolving refining-furnace bymeans of oxides of iron. The operation continues until the carbon showssigns of oxidation. It must then be stopped, partly on account of thereducing action of the carbonic oxide on the phosphates formed andpartly because the iron must retain all or nearly all its carbon to keepit fluid for transfer from the refiningfurnace to the steel-furnace; butit is found that silicon and manganese are much more quickly oxidizedthan phosphorus, for while mere traces of the former elements remain inthe bath a considerable portion of the latter is yet present at the timewhen the operation must be stopped. Forinstance, a pig containingphosphorus, 2.50 per cent, with the usual amounts of silicon andmanganese, will retain practically no silicon or manganese; but as muchas 0.75 per cent. of phosphorus will yet be in the bath when, accordingto the Bell- Krupp method, the refined pig-iron must be transferred.

Myimprovement consists in treatingthe bath in such amanner that afterthe Bell-Krupp process has been performed a new refining operation maybecarried on in the same furnace, by which nearly all the phosphorus willbe removed, even when the most highly phosphoric pigs areemployed,thusmaking them available for the manufacture of fine steels.In order to attain this result I commence the operation in the usualmanner as performed in the Bell- Krupp process. I prefer, however, arevolvin g to a rocking refining-furnace as more convenient in practiceand more efficacious in its working. Having conducted the operation to(N0 model.)

its end as now performed-Le, when carbonic oxide begins to burnIpreferably draw off the sla This removes with the slag all thephosphorus that has been oxidized and eliminated from the iron. Then,instead of drawing off the charge at this moment, as Bell and Krupp do,I add into the furnace a certain amount of oxidizable materials,such assilicon and manganese, in a melted state.

I have found that in basically-lined vessels silicon has a decidedeffect in the removal of phosphorus when added at the proper timei. 0.,after a part of the phosphorus has already been removed. Its addition tothe bath at this period, on account of its greater affinity for oxygen,retards the formation of carbonic oxide, which, having a strong reducingaction on the phosphates in the slag, would cause a reabsorption ofphosphorus into the iron if the operation were not immediately stopped.Manganese has also, to a lesser degree, the same effect, and as,moreover, its effect on basic linings is less deleterious than that ofsilicon, it may be employed with advantage in connection with it for thepurpose mentioned, in order to temper the strong cut ting action ofsilicon and to add to the fluidity of the slag, which, as it must bethoroughly separated from the refined pig, should be as liquid aspossible. I so proportion the additions that after they are in thebaththe metal has nearly the same composition, as when first run intothe furnace, with the exception of phosphorus, a notable quantity ofwhich has been removed by the first opera: tion.

The hearth is then revolved rapidly roe a period extending from two toeight min-g utes, and the operation is stopped as soon as the flameshows that the carbon in the iron is beginning to burn.

I prefer to use for additions such compounds of iron and silicon, or ofiron, silicon, and manganese, as may be found among the pigirons ofcommerce. These, of course, may vary in composition, the main objectbeing to introduce a certain amount of silicon in all cases and acertain amount of manganese when judged necessary. Any silicious pigironmay be used, with or without the addition of a small quantity offerro-mangauese.

The compound of silicon, manganese, and iron, known under the name offerro-silicon, may also be used advantageously.

To better explain the operation, I will suppose that the pig to betreated contains phosphorus, 2.50; silicon, 1.00; manganese, 0.50. Ifirst place it in a furnace lined with oxide of iron, as in theBelLKrupp method, and carry the operation to its usual termination aspracticed in this methodi. 0., when carbon begins to burn. The pig thencontains traces of silicon and manganese, and about 0.75 per cent.phosphorus, which renders it unfit for the manufacture of steel,although the Bell- Krupp method has been carried out to its fulldevelopment. I then, by preference, draw off the slag if it appears tohave accumulated on top of the bath in a dangerous quantity, (instead ofdrawing ott' the charge and transferring it to the steel-making furnace,as in the Krupp or Bell processes,) and immediately run in the necessaryadditions, as aforesaid, to remove the remaining phosphorus. greaterpart of the phosphorus has already been oxidized, it is not necessary toadd to the bath as much silicon as it originally contained. For thatreason the additions may consist of a certain quantity of silioious pig,sntficient to give to the charge in the furnace from 0.20 to 0.50 insilicon, and, especially if the lining seems loose or worn, a smallquantity of ferromanganese to give the charge about 0.25 per cent. inmanganese. The same amount of these ingredients may be introduced in theform of ferro-silicon, as before mentioned. The composition of the metalin the furnace will be phosphorus, 0.75; manganese, 0.25, and silicon,0.20 to 0.50.. The purifying operation is continued, and the silicon andmanganese will preserve the carbon from oxidation, and an additionalquantity of phosphorus will be removed from the iron before thereducingaction of carbonic oxide can take place. I revolve the furnace,and when the carbon begins to burn I stop this second operation and drawoff the charge. The metal will then have about the followingcomposition: phosphorus, 0.05 to 0.12; silicon and manganese,

traces; and it can be used for the manufacture of steel in theopen-hearth furnace. It is evident that this additional operation can beperformed several times successively, if necessary, each successiveoperation removing As the more phosphorus. It can be applied tocomparatively pure pigs when it is desirable that a greater quantity ofphosphorus should be removed.

I am aware that ferro-silicon and silicon and manganese have been usedbefore in the mannfacture of the so-called Terrenoire phosphorus steel,and also in making solid steel castings; but they have never beenemployed as a second charge in a basically-lined vessel to retard oravoid the reducing action of carbonic oxide in the elimination ofphosphorus from a melted bath of crude iron, and to prevent the reducingback into the iron of the oxidized phosphorus retained in the slag.

In the steel-making processes before named, where silicon and manganeseare used, their action is intended to neutralize the phosphorus which ispresent in the steel; but it does not remove it.

My process is not, primarily, for making steel, (although the principleon which it rests may be used in the manufacture of steel fromphosphoric pig in basically-lined hearths,) but it is for furthertreating and purifying a bath of impure crude cast-iron and preparing itthoroughly for the manufacture of steel.

I do not claim the first stages of my process, as those have been used,my invention only relating to the complete process, including the secondstages.

I claim as my invention- The process specified for treating iron for theremoval of phosphorus and other impurities and the production of purecast-iron, consisting in introducii'ig the melted metal. upon abasic-lined hearth, and allowing the principal portion of the impuritiesto become oxidized in the form of slag, the carbon remaining unacted on,or nearly so, and then adding silicon or manganese, or equivalent easilyoxidized material, while the iron is still on a basic hearth, forcombining with or facilitating the separation of the remainingimpurities, and then separating the iron and slag before the carbon ofthe iron is burned, substantially as specified.

Signed by me this 20th day of April, A. D. 1880.

L. G. LAUREAU. \Vitnesses A. L. HOLLEY, G no. 'I. IINGKNEY

